Refrigerating apparatus which perform a vapor compression refrigerating cycle have been known in the prior art. This type of refrigerating apparatus has been used widely as air conditioners for room cooling and heating, and cooling apparatus such as refrigerators and freezers for the storage of foods. In this refrigerating apparatus, the refrigerant discharged from the compressor flows, in sequence, in a condenser, an expansion mechanism, and an evaporator in the refrigerant circuit, whereby a vapor compression refrigerating cycle is executed.
In the refrigerant circuit, not only refrigerant but also refrigerating machine oil for lubricating the inside of a compressor is discharged from the compressor. Japanese Patent Application Kokai No. (2001)280719 shows a technique for reclaiming such discharged refrigerating machine oil and returning it to the compressor. More specifically, an oil separator, disposed on the discharge side of the compressor, is connected, via an oil return passage way, to a suction pipe of the compressor. Usually, a switching valve is inserted in the oil return passage way. In this arrangement, by placing the switching valve in the opened position, the refrigerating machine oil separated from discharged gas refrigerant in the oil separator is returned, via the oil return passage way and the suction pipe, to the compressor.
Problems To Be Solved
However, all of the refrigerating machine oil contained in the discharged gas refrigerant is not brought back to the compressor by the oil separator, in other words some refrigerating machine oil will circulate through the refrigerant circuit together with the refrigerant. And, with the elapse of time since the refrigerant was circulated through the refrigerant circuit, refrigerating machine oil accumulates little by little in the evaporator. To cope with the accumulation of refrigerating machine oil in the evaporator, in a conventional refrigerating apparatus of the type which uses, as an expansion mechanism, a valve-travel controllable expansion mechanism such as an electric expansion valve, the expansion valve is opened a little more than usual to allow a large amount of liquid refrigerant to flow through the evaporator so that a wettish operation is carried out, in order to reclaim refrigerating machine oil that has accumulated in the evaporator and return it to the compressor.
In spite of such arrangement, if the expansion mechanism is implemented by an expansion valve of the temperature sensitive type, this makes it difficult to perform a wet operation by forcibly controlling the valve travel, and it is also difficult to reclaim refrigerating machine oil from the evaporator to the compressor.
Bearing in mind these problems, the present invention was made. Accordingly, an object of the present invention is to provide a refrigerating apparatus employing, as an expansion mechanism, a temperature sensitive expansion valve, in which refrigerating machine oil that has accumulated in the evaporator is brought back to the compressor.